Dual schedule ignition system

ABSTRACT

An ignition system for an internal combustion engine, such as an outboard marine engine, which includes an advanced timing schedule, a normal timing schedule, and a circuit for switching between the two schedules or disabling both schedules based upon engine operating conditions. The ignition system includes an optoelectronic time base generator which produces two sets of timing pulses relative to crankshaft position which are normal timing pulses and advanced timing pulses. The time base generator comprises a LED-phototransistor pair and an encoder disk attached to the crankshaft with slots to interrupt the emission path between LED-phototransistor pair. The normal pulses are generated based upon the trailing edge of each slot while the advanced pulses are generated based up the leading edge, wherein the width of the slots indicate the degree of advancement of the advanced schedule over the normal schedule. Both schedules are inhibited based on a high overspeed condition and a low overspeed condition when the engine is overheated, wherein there is a smooth tarnsition between the two conditions.

CROSS-REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 315,147, filed Feb. 24, 1989,now U.S. Pat. No. 4,957,091, and is a continuation-in-part of U.S.patent application entitled "Electronically Assisted Engine StartingMeans," Ser. No. 131,457, filed on Dec. 11, 1987, now U.S. Pat. No.4,858,585, by the same inventive entity, which is also commonlyassigned.

FIELD OF THE INVENTION

The present invention pertains generally to an electronic ignitionsystem for an internal combustion engine, such as an outboard marineengine or the like, and is more particularly directed to a dual scheduleignition system having normal and advanced timing schedules with a timebase generator for generating two trains of pulses where the first pulsetrain is advanced a predetermined number of degrees of engine rotationwith respect to the second pulse train.

BACKGROUND OF THE INVENTION

Previously, outboard marine engines have often utilized various meansfor accomplishing easier starting. For example, such engines may engagea "warm-up" lever which manually advances the ignition timing andpartially opens the carburetor throttle plates. The function of sucharrangement is to increase the idle speed and the air/fuel ratio of theengine when it is started. These conditions allow the engine to starteasier and run more smoothly until it has warmed up to its standardoperating temperature.

While many other engine ignition systems have utilized various means toselectively advance the ignition timing characteristic during operation,none of these systems has been adapted to selectively change the enginetiming characteristic as a function of the temperature of the engineduring its warm-up phase, as well as during a predetermined time periodregardless of the temperature of the engine, and as a function of theoperating speed of the engine, particularly when operated at arelatively high speed.

A multi-variable ignition system for outboard marine engines or thelike, which selectively adapts ignition scheduling on this basis isillustrated in the referenced parent application, U.S. patentapplication Ser. No. 131,457, entitled, "Electronically Assisted EngineStarting Means" by Gregry M. Remmers, which was filed on Dec. 11, 1987,and which is assigned to the assignee of the present invention. Thedisclosure of Remmers is hereby expressly incorporated by referenceherein.

The system of Remmers provides an improved ignition system whichutilizes a signal proportional to the speed of the engine and couplessuch speed signal with other signals representing additional engineoperating conditions to selectively modify the ignition timingcharacteristic of the engine to accomplish the functional operationalcharacteristics of: (1) providing protection against engine damage thatmay be caused by a runaway speed condition; (2) providing a desirableignition advance during the warm-up period of the engine; (3) providinga desirable ignition advance during the initial engine start up period,irrespective of the temperature of the engine (i.e., even when theengine is warm as a result of having been previously operated); and (4)providing protection against damage that may be caused by advancing thetiming characteristic while operating the engine above a predeterminedoperating speed.

The system as taught in Remmers, while advantageous in the adjustment ofignition timing in dependence on a variety of engine operatingconditions, does not exhibit the most advantageous time base generatoror means for distributing the ignition pulses. The time base for thatsystem is derived from two sets of coils, each of which is associatedwith a particular cylinder and crankshaft position. One set of coils isphysically advanced with respect to the other set to generate two setsof timing pulses; one a normal pulse train and the other an advancedpulse train. Magnets on the flywheel or crankshaft fire each coil insuccession to generate the two pulse trains, and engine operatingconditions are combined to determine which set of pulses is used toignite the engine.

Such time base generator is simple and easy to use in small engines, butwith higher displacement engines two ignition coils per cylinder becomessomewhat more difficult to package. Further, for multiple cylinderengines, those with four or more cylinders, it is desireable to producea schedule of ignition advance based on a plurality of engine operatingconditions, most typically, one that varies with throttle position. Thisscheduling is difficult to accomplish with a dual ignition coil timebase generator.

Moreover, in Remmers, when inhibiting ignition pulses relative tooverspeed and overheated engine conditions, an overspeed threshold isswitched immediately from one level to another level when an overheatedcondition occurs. For small displacement outboard marine engines, anoverheated engine condition many times results when the engine is underconsiderable load, usually pushing a boat along at a high rate of speed.Inhibiting the ignition pulses without any transition between thethreshold levels under these conditions can cause a rapid anddisconcerting deceleration. Therefore, it would be advantageous toprovide a slower transition between the threshold levels so that, if anoverheated condition occurs during such a high load condition, a slowerand more acceptable deceleration will occur.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide an improvedelectronic ignition system for an internal combustion engine.

Another object of the invention is to provide an improved ignitionsystem which includes an advanced timing schedule, a normal timingschedule and a circuit for switching between the two schedules, ordisabling both schedules, based upon different combinations of engineoperating conditions.

Yet another object of the invention is to provide a time base generatorfor an ignition system which has an optical encoder rotatingsynchronously with crankshaft position and generating pulses based uponphysical timing features of the encoder, wherein the width of a timingfeature is determinative of an ignition advance.

Still another object of the invention is to provide an improved ignitionsystem which disables the ignition schedules based on a high overspeedcondition and a low overspeed condition when the engine is overheated,wherein there is a smooth transition between the two conditions.

Accordingly, the invention provides an improved ignition system forinternal combustion engines, such as outboard marine engines, or thelike. The ignition system includes a time base generator for providing afirst train of pulses advanced in time from a second train of pulses.Each train of pulses is variable according to a schedule with respect tovarious engine operating parameters, most particularly throttleposition.

The time base generator operates by rotating an encoder disk with timingfeatures past an illumination source which is optically coupled to aphoto-sensitive element. The timing features are positioned on the disksuch that each feature is a predetermined number of degrees of enginerotation in duration. A digital waveform is generated indicating thepresence or absence of a particular feature and two pulse trains arederived from the waveform, where the first is indicative of the leadingedge of the feature and the second is indicative of the trailing edge ofthe feature.

When the encoder disk is rotated in synchronism with the enginecrankshaft, two trains of pulses forming a time base are generated whereone pulse train is advanced over the second pulse train by the durationof each timing feature. The timing of the pulse trains relative toactual crankshaft position is varied by movement of the illuminationsource and photo-sensitive element relative to the encoder disk and isscheduled based upon various engine operating parameters.

The first train of pulses provides an advanced ignition timing schedulewhile the second train of pulses provides a normal ignition timingschedule. An electrical pulse generator and distributor receives the twopulse trains and selects between the two based upon receiving an advancesignal or a normal signal. Alternatively, both schedules are inhibitedby an inhibit signal. The selected pulse schedule is distributed to thecorrect cylinders in the firing sequence of the engine to ignite theengine.

A control circuit generates the advance, normal, and inhibit signalsbased upon time, engine temperature, and starting condition. Preferably,the advance signal is generated during the starting of the engine andfor a short predetermined period thereafter. If the engine is not thenoperating above a warm up temperature, the advance signal is continueduntil this condition occurs. Regardless of the warm-up status and timeof running, if the engine is being operated in excess of a first enginespeed, the normal signal is generated. In addition, if a third enginespeed is exceeded, the inhibit signal is generated disabling ignitionpulses from both schedules. The inhibit signal is also generated if theengine exceeds a second speed and an overheated engine temperatureexists. The first speed is, in general, lower than the second speed,which is lower than the third speed. The overheat temperature is, ingeneral, higher than the warm-up temperature.

In a preferred embodiment, the inhibit signal for engine overspeed isgenerated from a comparator circuit which compares an engine speedsignal against an overspeed threshold. The overspeed threshold issmoothly lowered to a lower overspeed threshold when an overheatedcondition of the engine occurs, thus preventing rapid deceleration. Athreshold generating means is utilized to produce the thresholds and isimplemented by a voltage divider which provides a first thresholdvoltage which is representative of a high overspeed condition, forexample, approximately 6,700 RPM. The voltage divider is shunted by anoptically coupled device upon closure of a temperature sensor in theengine to produce a second threshold voltage representative of a lowoverspeed condition, for example, approximately 2500 RPM. A delay means,comprising a capacitor, is coupled to the output of the thresholdgenerating means and is generally charged to the first threshold. Whenthe temperature sensor operates, for example at approximately 212° F., adischarge path through the optically coupled device is provided whichproduces a smooth relatively long decay of the first threshold voltageto the second threshold voltage. A rapid charging path for the delaymeans is provided to ensure that, when the engine is turned off and thenimmediately restarted, the delay feature is present. The rapid chargingpath is disabled by another optically coupled device upon operation ofthe temperature sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features, and aspects of the invention will bebetter understood and more fully described upon reading the followingdetailed description in conjunction with the appended drawings wherein:

FIG. 1 is a partially-broken, pictorial perspective view of an internalcombustion engine of the outboard marine type illustrating a time basegenerator constructed in accordance with the invention;

FIG. 2 is a cross-sectional view of a first position of the time basegenerator illustrated in FIG. 1 taken along section line 2--2 of thatfigure;

FIG. 3 is a cross-sectional view of a second position of the time basegenerator illustrated in FIG. I taken along section line 2--3 of thatfigure;

FIG. 4 is a pictorial representation of various timing waveforms outputfrom the time base generator illustrated in FIG. 1 and the pulsegenerator and distributor illustrated in FIG. 5;

FIG. 5 is system block diagram of an ignition system constructed inaccordance with the invention;

FIG. 6 is a graphical representation of the dual ignition schedules as afunction of a plurality of engine operating parameters for the systemillustrated in FIG. 5;

FIG. 7 is a detailed electrical schematic diagram of the control circuitillustrated in FIG. 5;

FIG. 8 is a detailed electrical schematic diagram of the pulse generatorand distributor circuit illustrated in FIG. 5; and

FIG. 9 is a detailed electrical schematic diagram of the capacitivedischarge circuits illustrated in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The time base generator 8 of the invention is shown to advantage in FIG.1 where the mechanism for the generation of two timing characteristicsor pulse trains is illustrated. The time base generator 8 includes agenerally cylindrically shaped encoder disk 10 which is bolted onto ashaft extension 12 of the crankshaft of an internal combustion engine soas to cause the disk to rotate synchronously therewith. The crankshaftextension 12 includes a notch 14 which is received in a reciprocallyshaped hub 13 of the encoder disk 10. The notch 14 positions the encoderdisk 10 and those timing features included thereon at a known crankshaftposition, i.e., at an angle relative to top dead center of a particularcylinder, for example, cylinder 1. To assist in timing the engine, thisreference point 0° can be inscribed on the encoder disk 10 so that itcan be aligned with a stationary mark on the engine casing by the commonstrobe light technique. Rotation of the crankshaft is clockwise whenviewed from the top (front) of the engine, as is conventional with mostinternal combustion engines.

The encoding disk 10 has an encoding portion with several timingfeatures located at spaced positions around its periphery. The timingfeatures in the illustrated implementation are provided as slots 16, 18and 20, although many other geometric features would suffice. In thepreferred embodiment, the number of slots is equal to the number ofcylinders of the engine and they are equally spaced around the peripheryof the encoder disk 10. For a six-cylinder, two cycle engine this meanssix equally spaced slots at 60° intervals. It is evident that for asix-cylinder, four cycle engine, the slots would be spaced at 120°intervals and there would be three in number.

Each of the slots 16, 18 and 20 has a width which is a particularangular rotation of the crankshaft, in the preferred implementation,15°. The encoder disk 10 further includes a synchronizing portion havinga timing feature, slot 22, to indicate the relative position of the disk10 with respect to overall crankshaft position, thus associating eachslot 16, 18, and 20 with a particular cylinder. In the illustration,slot 22 is placed in advance of cylinder 1 top dead center and slots 16,18, and 20 correspond to cylinders 6, 1 and 2, respectively.

As better shown in FIGS. 2 and 3, the timing features of the encoderdisk 10 make and break the optical illumination path between an LED 26and two phototransistors 28 and 30 which are mounted in anoptical-coupler block 32. The optical-coupler block 32 is mounted on atiming ring 15 which slidably rotates on the shoulder of a raised boss17 of the engine. Spring clips 19, 21, 23 retain the ring 15 in the boss17 without preventing its rotation. An extension arm 40 of the timingring 15 is used to rotate the ring 15 and thus optical-coupler block 32with respect to the fixed relationship of the encoder disk 10 and thecrankshaft.

Normally, the ring 15 is biased to a setable position by spring 43 whereit abuts an adjustable stop 45. An ignition advance assembly 41including a roller 42 can be used to apply force against a cam surface47 of the arm 40 in order to rotate the optical-coupler block 32 independence upon a plurality of engine operating conditions to scheduleignition timing. Such engine operating conditions could be such thingsas speed, airflow, water or engine temperature, humidity, manifoldpressure, altitude, throttle position, etc.

From FIG. 2, it should be evident that during the rotation of theencoder disk 10 by the crankshaft, illuminating radiation from the LED26 to the phototransistor 28 is normally blocked until a slot, forexample, the one indicated as 18, rotates between the LED 26 and thephototransistor 28. At this time, the optical transmission path is open,and the phototransistor 28 conducts current producing an electricalsignal indicating the presence of the slot. During this time the opticaltransmission path to the upper phototransistor 30 is blocked by theencoder casing. However, during those times when the slot 22 rotatesinto a position between the LED 26 and the phototransistor 30 as shownin FIG. 3, the open transmission path causes phototransistor 30 toconduct current and produce an electrical signal indicating the presenceof the synchronizing slot 22 at the position of the optical-couplerblock 32.

In general, the timing signals generated from the time base generatorare shown in FIG. 4. The first signal is a SYNCH signal (FIG. 4A) fromslot 22 which is approximately 10° in duration and occurs once for every360° of engine crankshaft rotation. The leading edge of the SYNCH signaloccurs some advancement before top dead center of a particular cylinder,in the illustrated example, cylinder 1. From this leading edge referencepoint, all other timing pulses and signals for the system can bemeasured. In general, the SYNC signal is used to reset the distributionsequence of the ignition pulses. The second timing signal CYL is a groupof pulses forming a square wave which is generated from the encoderslots 16, 18, 20, etc. (shown in FIG. 4B). There is a pulse, CYL1-CYL6,respectively, for each cylinder of the engine. The pulses are 15° ofengine rotation in duration and separated by equal angular increments ofthe crankshaft at 60° intervals.

From the pulses of FIG. 4B, two sets of ignition pulses are generated bythe pulse generator and distributor 70 as shown in FIG. 4C. The leadingedge of each cylinder pulse, CYL1-CYL6, is used to generate one train ofadvanced pulses A, and the trailing edge of each cylinder pulse is usedto generate a second train of normal pulses N. The advanced pulse trainA is used in an advanced timing schedule and the normal pulse train N isused for a normal timing schedule as will be more fully describedhereinafter.

In the preferred embodiment, the normal pulses at idle are at top deadcenter of each associated cylinder, while the advanced pulses areadvanced over the normal pulses a predetermined increment, 15°. It isseen that the width of the encoder slots 16, 18 and 20 determines thepredetermined advancement of the advanced schedule over the normalschedule. Further, the position of the optical-coupler block 32 relativeto the fixed relationship of the encoder disk 10 and crankshaftdetermines the variance of timing with respect to engine operatingvariables and, thus the actual timing schedule.

An improved ignition system using the time base generator 8 illustratedin FIGS. 1-4 is more fully shown in the block diagram with reference toFIG. 5. The ignition system includes a pulse generator and distributor70 which produces a trigger pulses TRG to a number of capacitivedischarge circuits 71-76, wherein each capacitive discharge circuit isassociated with a particular cylinder. When enabled from the pulsegenerator and distributor 70 by individual enable lines EN1-EN6, atrigger pulse TRG will cause a capacitive discharge circuit 71-76 toprovide a high current, low voltage pulse of approximately 300V throughthe primary of a step-up transformer 77-82, respectively. The step-uptransformers 77-82 step up the voltage of the current pulses from thecapacitive discharge circuits into high tension pulses which fire sparkplugs 83-88, respectively, of an associated cylinders of the engine. Thespark plugs 83-88 are ignited sequentially in the firing order of theengine by their respective connection in that order relative to thesequence of firings of the capacitive discharge circuits.

The time base generator 89 is shown generating the pulse trains SYNC andCYL to the pulse generator and distributor 70, which are the signals asshown in FIG. 4A and 4B. The trigger pulses TRG which are derived fromthese signal by the pulse generator and distributor 70 are those asshown in FIG. 4C. They are distributed by generating the enable signalsEN1-EN6 based on crankshaft position and the firing order of the engine.Whether the trigger pulses TRG are the advanced schedule A or the normalschedule N, depends upon a control circuit 90.

The control circuit 90 determines from the engine operating conditionsincluding means for sensing RPM 92, means for sensing an overheatcondition 94, means for sensing a warmup condition 96, and means forsensing a starting condition 98 whether the advanced timing schedule,the normal timing schedule, or no timing schedule should be used. Thisselection information is delivered to the pulse generator anddistributor 70 via an ADVANCE/NORMAL signal on line 99. Alternatively,the control circuit 90 generates an INHIBIT signal on line 101 tocompletely stop any ignition pulses from being generated to the engine.

FIG. 6 is a graphical representation of the advanced timing schedule 91and the normal timing schedule 93 illustrating an + advance angle beforetop dead center (TDC) as a function of an engine operating parameter, orcombination of parameters. In the preferred embodiment, the schedulesare a similar function of throttle position. While more complexschedules can be used, outboard marine engines advantageously advanceignition timing based on throttle position.

The advanced timing schedule 91 is used during starting and warmupdurations, while the normal timing schedule 93 is used at all othertimes, except in those instances when both ignition schedules areinhibited. It is seen that there is always a +15° advance between theadvanced schedule and the normal schedule which is dependent upon thespacing between pulse trains A and N from the time base generator 8. Thespacing between the pulses is due to the slot widths of the opticalencoder disk 10. The variation in advance angle as a function of engineoperating parameters (schedule) is developed by the rotation of theoptical-coupler block 32 relative to the fixed position of the opticalencoder disk 10 on the crankshaft. The functions or schedules shown inFIG. 6 are generally the same for the advanced timing schedule and thenormal timing schedule and monotonically increase with increase inthrottle position. However, these can be very complex schedulesdepending upon the shape of the cam surface which displaces the arm 40to cause the rotation of the timing ring 15 and the relative movement ofthe optical-coupler block 32 with respect to the encoder disk 10.

The control circuit 90 will now be more fully described with respect tothe detailed electrical schematic of FIG. 7. The power supply of thepresent ignition system, indicated generally at 64, includes lines 66and 68 which are connected to a stator coil 71 of an alternator and to afull-wave rectifier bridge 70. Several magnets on the engine flywheel(not shown) induce a voltage in the stator coil 71 as the flywheelturns, which voltage is rectified by the bridge 70. Overvoltageprotection is provided by the connection of a triac 72 between lines 66and 68. The power supply 64 generally provides approximately a +20Voutput on line 74. The +20V output is further regulated by NPNtransistor 76 having a Zener diode 78 and bias resistor 79 connected toits base. The transistor 76 provides a +15V regulated supply on line 80.This +15 volt regulated supply line 80 is additionally coupled to thepower supply line of the capacitive discharge circuits 71-76.

The stator coil 71 produces six pulses for every revolution of theflywheel and thereby provides tachometer pulses on line 86 which arecoupled through a capacitor 82 and resistor 84 to the frequency input(F/I) of a frequency to voltage converter 88. The frequency to voltageconverter 88 has an output OUT which generates a voltage level on line90 that is directly proportional to the frequency of the pulses, andhence RPM of the engine. A variable resistor 92 and a fixed resistor 94define a voltage divider that is adjustable to vary the level of theoutput voltage produced on the output line 90 for a particular voltage.

One feature of the control circuit 90 provides protection against arunaway speed condition occurring during operation of the engine. Thisis accomplished by utilizing the voltage level generated by converter 88on line 90 to inhibit the ignition pulses. The voltage on line 90 isconnected to the inverting input of a comparator 96 through resistor 98and line 100. The noninverting input of the comparator 96 receives areference voltage on line 102 against which the voltage on line 100 iscompared. The output line 104 of the comparator 96 makes a transition toa low logic level (approximately 0 volts) when the voltage on the inputline 100 is greater than the reference voltage on line 102.

For an operating condition that does not represent an overheatedcondition of the engine, the voltage level on line 102 is designed to beapproximately +5 volts. The +5 volts on line 102 is supplied by thepower supply from line 80 through voltage dividing circuitry. Line 80 isconnected through a resistor 106 to a line 108 that is connected to aZener diode 110 to provide a regulated voltage of approximately +9V online 108. Line 108 is connected to resistors 112 and 114 which functionas a voltage divider to provide a voltage of approximately +5 volts on aline 116. The line 116 is connected to the line 102 through a resistor118 and applies the reference +5V to the noninverting input of thecomparator 96. A low logic level on line 104 is inverted by an invertor105 (FIG. 8) to produce a high logic level disabling signal, the INHIBITsignal, to the pulse generator and distributor circuit 70.

During operation, the converter 88 produces a voltage on the output line90 which is supplied to the inverting input of comparator 96. When thespeed reaches approximately 6,700 RPM, the comparator 96, aftercomparing the voltage output to the reference voltage of approximately+5V, produces a low logic level on the output line 104 that results inthe disabling INHIBIT signal. Protection against a runaway speedcondition is thereby provided by a relatively few number of circuitcomponents.

It should be understood that the disabling of the ignition pulses mayoccur for an incremental short period of time and on a cyclic basis. Ifthe speed is close to the over speed condition, as soon as an overspeedcondition is detected, the inhibiting will occur and the speed willquickly drop because of the lack of ignition pulses. When the operatingspeed falls below the threshold, the INHIBIT signal will be switched offand the ignition pulses will no longer be disabled. Thus, as a practicalmatter, the engine speed may be modulated around the threshold speedthat triggers the comparator 96.

In accordance with another aspect of the control circuit 90, the maximumspeed of operation is reduced from approximately 6,700 RPM toapproximately 2,500 RPM when an overheated engine condition is detected.This is accomplished using the same comparator 96 in combination withtemperature sensing circuitry for the engine. In this regard, lightemitting diodes (LEDs) 124 and 126 are optically coupled to phototriacs125 and 127, respectively. The LEDs 124 and 126 are connected to the+20V supply on line 74 through resistor 128, and to ground through adiode 130 and an overheat temperature switch 132. The overheattemperature switch 132 is a bimetallic switch positioned in the head ofthe engine to sense the engine temperature. The switch 132 is adapted toclose at a temperature of approximately 212° F., and when closedprovides a conduction path through LEDs 124 and 126 placing thephototriacs 125 and 127 into conduction.

This operation lowers the reference voltage applied to the noninvertinginput of the comparator 96 to approximately 2.0V. The lower referencevoltage results in the INHIBIT signal being produced on line 104 at alower operating speed, as is intended. In operation, when an overheatedcondition is detected, the comparator 96 switches to a low logic levelat an operating speed of about 2,500 RPM and disables the ignitionpulses to limit the speed as previously described. The speed limiting,however, takes place at a lower speed limit of 2,500 RPM rather than theupper speed limit of 6,700 RPM.

The nature of the phototriac 125 is such that it will not be turned offuntil power is removed from the circuit, which will not occur until theengine is turned off. This feature is desirable in that it prevents thecircuitry from cycling on and off at or about the critical overheattemperature. However, to prevent an abrupt change in the overspeedthreshold when the overheat switch 132 closes, there is provided acapacitor 129 connected to the noninverting input of comparator 96.Normally, the capacitor 129 is charged up to the upper threshold voltageof +5V. When an overheat condition occurs, the capacitor 129 graduallydischarges through phototriac 125 and resistor 131 to ground.Preferably, the discharge path lowers the voltage at a predeterminedrate which is exponential in the illustration, but which could be anyfunction of time, for example, linear. The time constant of thedischarge path is long enough, about 4-10 secs., to produce a smoothtransition between the upper and lower threshold speed limits and, as aconsequence, a gradual deceleration of a boat or other water vehiclepowered by the engine. The capacitor 129 is charged rapidly to the upperthreshold voltage at start-up by a resistor 135 and diode 133. Thiscurrent path is shunted to ground and disabled by phototriac 127 duringan overheat condition.

Another attribute of the present control circuit 90 includes theprovision of automatically providing an advanced timing schedule oradvanced ignition characteristic when the engine is initially startedand until the engine reaches a predetermined minimum warm uptemperature, unless a specific engine RPM is exceeded. With respect tothe warm-up aspect of the circuit operation, a line 134 is connectedthrough a warm-up switch 136 to ground. The switch 136, which is abimetallic sensor, closes when the sensed engine temperature exceeds awarmup temperature, within the range of about 90° F. to 100° F. The line134 is normally high (open) but makes a transition to a low logic level(ground) when the engine warms up sufficiently to close the switch 136.The line 134 is connected to the +20V supply through an LED 135 andresistors 137 and 139. The LED 135 is optically coupled to a phototriac141 which is connected to the noninverting input of a comparator 140 viaa resistor 142. The comparator 140 provides a high logic level output online 144 when switch 136 is not closed.

The output line 144 of comparator 140 is connected to the noninvertinginput of a comparator 148 which acts as an AND gate. Another input line152 to the comparator 148 is normally high until a predetermined speedis reached by the engine as will be subsequently described. Thecomparator 148 provides a high logic level output on line 154 only whenthe input lines 146 and 152 are both at a high logic levels. When theline 154 is a high logic level, the ADVANCE signal is generated and theadvanced timing characteristic output to the capacitive dischargecircuits. When the output on line 154 is a low logic level, the NORMALsignal is generated and the normal timing characteristic output to thedischarge circuits.

It will be understood from the foregoing that the engine will beoperated with the advanced timing characteristic until the engine warmsup to an operating temperature of about 90° to 100°. When warmup switch136 closes, the output 144 will be pulled to a low logic level therebyswitching the comparator 148 to a low logic level and producingoperation by the normal ignition timing characteristic.

However, the engine will also operate in its advanced timingcharacteristic during start up and for a short predetermined periodafter initial start up, i.e., for approximately 5 to 10 seconds,regardless of the temperature of the engine. This is accomplished byhaving the starter solenoid 155 apply the battery voltage B+ to acapacitor 160 via line 162, a diode 164 and a line 166 when the ignitionswitch is closed. Line 162 is connected to the noninverting input of thecomparator 140 via a resistor 167. Upon starting of the engine, thebattery voltage B+ will charge the capacitor 160 and provide a highlogic level on the input line 138 to place the engine in the advancedtiming characteristic mode of operation during the starting period ofthe engine and for the time period required to discharge the capacitor160 to a level where the comparator 140 switches to a low output. In theillustrated embodiment, this is preferably about 7 seconds, although thecircuit components can be chosen to provide a longer or shorter timeperiod if desired.

In accordance with yet another aspect of the present control circuit 90,provision is made to automatically inhibit the advanced timingcharacteristic when the operating speed of the engine exceeds apredetermined level of approximately 1,500 RPM. This characteristic isto prevent operation of the engine with an ignition advance above thisspeed which could result in damage to the engine.

To inhibit the advanced timing characteristic, the voltage fromconverter 88 on output line 90 is connected to the inverting input 100of a comparator 170 on line 100. The noninverting input of thecomparator 170 is connected to the +5V reference supply line 116 via aresistor 174. The reference voltage is chosen to cause the comparator tohave its output line 176 switched to a low logic level when the speedvoltage increases to level equal to an operating speed of approximately1,500 RPM. When the output line 176 is at a low logic level, it removesthe high logic level applied to the comparator 148 thereby causing it toswitch to a low logic level and disabling the ADVANCE signal to removethe engine from its advanced timing characteristic mode of operation.Thus, the circuitry always prohibits operation in an advanced timingmode above approximately 1,500 RPM, even if the engine is not warmed upor is still within the start-up period of approximately 7 seconds afterstaring.

The power for operating the control circuit 90 is obtained from avoltage induced in the stator coil 71 that is regulated by the powercircuitry. During the initial start-up period, the cranking speed maynot be sufficient to provide reliable voltage levels to ensure correctcircuit operation. Provision is made to supplement the output of thepower supply with the battery voltage B+ from the starter solenoidduring cranking. This is accomplished by coupling the battery voltage B+on line 166 to line 74 via diode 164, line 162 and diode 180.

FIG. 8 illustrates the detailed electrical schematic of the pulsegenerator and distributor circuit 70. In general operation the pulsegenerator and distribution circuit 70 performs three functions.Initially, it generates the advanced pulse train A and the normal pulsetrain N from the CYL waveform. Secondly, the circuit selects between thepulse train A and pulse train B, or inhibits both pulse trains, based onthe input signals ADVANCE, NORMAL, and INHIBIT. Additionally, thecircuit generates the enabling signals, EN1-EN6 based on the SYNCwaveform and the CYL waveform to distribute the selected pulse train asthe TRG signal to the correct cylinders in the firing order of theengine.

The LED 26 is shown as being always powered on by its connection in aconductive path between +15V, the emitter-collector path of NPNtransistor 242, a resistor, and ground. The transistor 242 regulates thecurrent flow through LED 26 by having a predetermined bias voltage onits base. The bias voltage is generated by the combination of Zenerdiode 238 and resistor 240 connected between the +15V supply and ground.Phototransistors 28 and 30 generate the previously described signals CYLand SYNC when illuminated by LED 26.

The pulse generator and distributor circuit 70 comprises basically twomonostable multivibrators 200 and 202 and a synchronous sequentialcounter 222. Generally, the monostable 200 is configured to be triggeredby the positive going edge of a pulse to its TR+ input. Application ofan edge transition from a low logic level to a high logic level at inputTR+ will produce a positive going pulse from its Q output which becomesthe advanced pulse train A. Conversely, the monostable 202 is configuredto produce a positive going pulse from its Q output when a negativegoing edge of a pulse is applied to its TR- input, which results in thenormal pulse train N.

Both the TR+ input of monostable 200 and the TR- input of monostable 200are connected to the output of a NAND gate 220 which is configured as aninvertor and driven by the CYL signal. The CYL signal is generated bythe illumination of phototransistor 28 which is connected across bothinputs of the NAND gate 220. The NAND gate 220 has an open collectoroutput connected to the junction of a resistor 224 and a capacitor 226which inverts the CYL signal, thus providing a positive going transitionon the leading edge of the CYL signal and a negative going transition onthe trailing edge of the CYL signal. The ADVANCE and NORMAL signals arecombined into a single signal, ADVANCE/NORMAL, which is applied to thenegative true reset terminal R of monostable 200. The ADVANCE signal isthe high logic level of the combined signal while the NORMAL signal isthe low logic level.

With this circuit, two pulses are generated for each of CYL signal pulseand form two pulse trains, one based on the leading edges of the CYLsignal from monostable 200 and one based on the trailing edges of theCYL signal from monostable 202. If the advanced pulses are selected, theADVANCE/NORMAL signal is a high logic level and both pulse trains aretransmitted to the cylinders. Because the ignition circuit is acapacitive discharge circuit, the normal pulses which follow theadvanced pulses do not perform a retriggering of the ignition system asthe ignition capacitance has not yet recharged. If the normal pulses areselected, the ADVANCE/NORMAL signal is a low logic level which holdsmonostable 200 reset so that only the normal pulse train is generated.

The first pulse train A and the second pulse train N are combined in aOR gate 204 before being inverted by invertor 206. The output ofinvertor 206 is fed through OR gate 210 and finally inverted in invertor212 before becoming the trigger signal TRG. The INHIBIT signal isprovided through an invertor 105 and OR gate 208 to produce a disablingsignal at OR gate 210 during its presence. When the INHIBIT signal is alow logic level, a high logic level disables OR gate 210 and both pulsetrains.

Another inhibiting signal to OR gate 208 is provided by a D-typebistable 214 which has its *Q output connected to one of the inputs ofthe gate. The reset input R of bistable 214 is connected to the outputof invertor 216 whose input is connected to a resistor-capacitorcombination connected between +15V and ground. The set terminal S of thebistable 214 is connected to the SYNC signal at the output of NAND gate218. In operation, the bistable 214 which is reset on power up normallydisables the trigger pulses TRG until the first SYNC signal occurs. Thisis to prevent misfiring of the engine when initial engine rotationbegins and the ignition system is not yet synchronous with thecrankshaft. The capacitor 234 is generally charged up to +15V providinga normally low logic level on the reset input of the bistable 214. Thisproduces a high logic level output from the *Q output and thus disablesOR gate 210. When the first SYNC signal occurs, the bistable 214 is setremoving the disabling signal from OR gates 208 and 210.

The counter 222 generates the enabling signals EN1-EN6 sequentially fromits Q0-Q5 outputs, respectively. The enabling signals EN1-EN6 aregenerated in sequence and then cycled in the same sequence. The SYNCsignal caused by the illumination of phototransistor 30 is used to applya high logic level to the reset input RST of the counter 222. The SYNCsignal is inverted by NAND gate 218, resistor 228 and capacitor 230 inthe same manner the CYL signal was inverted The SYNC signal causes thecounter to reset and generate the ENI signal thereby arming therespective capacitive discharge circuit associated therewith. The pulsesA or N are then applied to the armed circuit firing the circuit inconcert with its respective crankshaft position After the trigger pulsehas been applied, the trailing edge of the *Q output of the monostable202 clocks the counter 222 by application of the *N pulses to its CLKinput. This advances the counter to the next enabling signal, EN2, andso on in the sequence until the cycle continues.

With reference to FIG. 9, the capacitive discharge circuits 71-76operate identically with respect to each of the cylinders which may bepresent in the engine. In the disclosed embodiment, there are sixcylinders and six discharge circuits, but only one of the circuits 76for the cylinders will be described in detail for the purpose ofclarity.

The six capacitive discharge circuits 71-76 are used to dischargealternate ignition capacitors 330 and 326 which are charged by therectification of charge coil pulses. The charge coil pulses for one bankare rectified by diode bridge 328 for capacitor 326 and the charge coilpulse for the other bank are rectified by diode bridge 332 for capacitor330.

When an ignition pulse TRG is passed through NAND gate 300 from line322, it will enable PNP transistor 302 to pass a pulse from a voltagesource on line 318 through diode 306. The voltage source on line 318 isthe regulated voltage +15V from the power supply as previouslydescribed. NAND gate 300 is armed by the pulse generator and distributor70 by the enable pulse, EN6. The resulting pulse which is produced bythe coincidence of the pulse signal TRG and the enabling level EN6 isdirected to the gate terminal of an SCR 316 to turn it on. The SCR 316when triggered into conduction, discharges one of the previously chargedignition capacitors 326 through circuit path from its anode, cathode,and line 320 attached to the primary of the ignition coil for cylindernumber 6.

To control the two timing schedules, the control circuit 90 eitherallows the advanced pulses and the normal pulses to be applied to theNAND gates or inhibits the advanced pulses so that only the normalpulses are applied to the NAND gates. This is accomplished by holdingadvanced monostable reset with a low logic level, the normal signal. Inaddition, for particular engine conditions, both sets of pulses areinhibited. Thus, an ignition system has been shown which can provide anadvanced schedule, a normal schedule or an inhibition of both schedulesbased upon engine operating conditions.

While a preferred embodiment of the invention has been illustrated, itwill be obvious to those skilled in the art that various modificationsand changes may be made thereto without departing from the spirit andscope of the invention as hereinafter defined in the appended claims.

What is claimed is:
 1. A time base generator for an ignition system ofan internal combustion engine having a crankshaft, said time basegenerator comprising:an encoder disk which rotates synchronously withthe crankshaft of the engine and includes a plurality of timing featuresof a predetermined width which are at fixed locations relative to thecrankshaft and includes at least one synchronizing feature which is at afixed location relative to the crankshaft and to at least one of saidtiming features; detector means for detecting the presence or absence ofsaid timing features and said at least one synchronizing feature and forgenerating digital signals representative thereof; and pulse generatingmeans for generating a first pulse train from the trailing edge of eachtiming feature represented in said digital signal and for generating asecond pulse train from the leading edge of each timing featurerepresented in said digital signal whereby the pulses of said secondpulse train are advanced from the pulses of said first pulse train by apredetermined angular rotation of the crankshaft determined by the widthof each timing feature.
 2. A time base generator as defined in claim 1wherein:said timing features are all of the same width.
 3. A time basegenerator as defined in claim 1 wherein:said timing features are not allof the same width.
 4. A time base generator as defined in claim 1wherein the internal combustion engine is a two-cycle engine andwherein:each timing feature corresponds to one cylinder of the engine.5. A time base generator as defined in claim 1 wherein the internalcombustion engine is a four-cycle engine and wherein:each timing featurecorresponds to two cylinders of the engine.
 6. A time base generator asdefined in claim 4 wherein:said synchronizing feature indicates apredetermined point in the firing order of the engine.
 7. A time basegenerator as defined in claim 6 wherein:every other of saidsynchronizing features indicates a predetermined point in the firingorder of the engine.
 8. A time base generator as defined in claim 1which further includes:means for mounting said detector means and forallowing movement of said detector means relative to the crankshaft andsaid fixed positions of said timing features.
 9. A time base generatoras defined in claim 8 wherein said means for mounting include:a mountingring concentric to the crankshaft which is adapted to rotate about thecrankshaft to vary the position of the detector means relative thereto.10. A time base generator as defined in claim 9 wherein said mountingmeans further include:means for rotating said mounting ring dependentlyupon at least one operating parameter of the engine.
 11. A time basegenerator as defined in claim 10 wherein:said at least one operatingparameter of the engine is the detected throttle position.
 12. A timebase generator as defined in claim 1 wherein:said encoder disk issubstantially cylindrical in shape and includes a timing portion havingsaid timing features implemented as timing slots about its periphery.13. A time base generator as defined in claim 12 wherein:said detectormeans includes a first emitter and first receiver of optical radiationcoupled through an optical path and located such that said timingfeatures make or break said optical path as said encoder disk rotates.14. A time base generator as defined in claim 13 wherein:said detectormeans further includes: a second emitter and second receiver of opticalradiation coupled though an optical path and located such that said atleast one synchronizing feature makes and breaks said optical path assaid encoder disk rotates.
 15. An ignition system for an internalcombustion engine of the type which has an ignition energy storagemeans, means for charging the ignition energy storage means, and meansfor discharging the ignition energy storage means in response to triggerpulses, the system comprising:trigger pulse generating means forproducing trigger pulses related to crankshaft position; and means forinhibiting the generation of said trigger pulses as a function of atleast one engine operating condition, said inhibiting means includingmeans for inhibiting said trigger pulses when the engine is operating inexcess of a first predetermined speed, means for inhibiting said triggerpulses when the engine is operating in excess of a second predeterminedspeed and in excess of a predetermined temperature wherein said secondpredetermined speed is less than said first predetermined speed, andmeans for delaying the inhibition of said trigger pulses at said secondpredetermined speed for a period of time after the engine reaches saidpredetermined temperature.
 16. An ignition system as set forth in claim15 wherein:said first predetermined speed is approximately 6,700 RPM.17. An ignition system as set forth in claim 16 wherein:said secondpredetermined speed is approximately 2,500 RPM.
 18. An ignition systemas set forth in claim 17 wherein:said predetermined temperature isapproximately 212° F.
 19. An ignition system as set forth in claim 18wherein:said period of time is at least approximately 4 seconds.
 20. Anignition system as set forth in claim 15 wherein said means forinhibiting include:means for generating an engine speed signal;temperature sensor means for generating a temperature signal when theengine is operating in excess of said predetermined temperature;threshold generating means for generating a high thresholdrepresentative of said first predetermined speed, if said temperaturesignal is not present, and for generating a low threshold representativeof said second predetermined speed, if said temperature signal ispresent; and comparator means being adapted to receive said engine speedsignal at a comparing terminal and said high and low thresholds at areference terminal, said comparator adapted to generate said inhibitingsignal if the engine speed signal is in excess of the threshold signalbeing applied to the reference terminal.
 21. An ignition system as setforth in claim 20 wherein said delay means includes:a capacitorconnected to said reference terminal which is initially charged to saidhigh threshold and discharges to said low threshold over saidpredetermined period of time when said engine temperature signal ispresent.
 22. An ignition system as set forth in claim 21 wherein:saidcapacitor has a relatively slow discharging path which is enabled whensaid temperature signal is present and a relatively fast charging pathwhich is disabled when said temperature signal is present.
 23. Anignition system as set forth in claim 22 which further includes:anoptically coupled device comprising a light emitting diode connected tosaid temperature sensor which is adapted to switch into conduction andenergize said light emitting diode when said sensed engine temperatureexceeds said predetermined temperature, said light emitting diode beingoptically coupled to a light sensitive switching device to switch saiddischarging path into conduction when said light emitting diode isenergized.
 24. An ignition system as set forth in claim 22 which furtherincludes:an optically coupled device comprising a light emitting diodeconnected to said temperature sensor which is adapted to switch intoconduction and energize said light emitting diode when said sensedengine temperature exceeds said predetermined temperature, said lightemitting diode being optically coupled to a light sensitive switchingdevice to switch said charging path out of conduction when said lightemitting diode is energized.
 25. An ignition system for an internalcombustion engine of the type which has an ignition energy storage meanscomprising:means for charging the ignition energy storage means; meansfor discharging the ignition energy storage means; means for detectingan overheated engine condition; and means for reducing the operatingspeed of the engine by inhibiting the discharging or charging of saidignition energy storage means, said reducing means reducing theoperating speed to no greater than a predetermined speed in the eventthat said overheated engine condition is detected while the engine isoperating above said predetermined speed, and including means forgradually reducing the engine operating speed to said predeterminedspeed.
 26. An ignition system as set forth in claim 25 wherein:saidpredetermined speed is approximately 2,500 RPM.
 27. An ignition systemas set forth in claim 25 wherein:said overheated engine condition is atemperature of approximately 212° F.
 28. An ignition system as set forthin claim 25 wherein:the period of time for the gradual reduction ofengine operating speed is at least approximately 4 seconds.
 29. Anignition system as set forth in claim 25 wherein said means for reducingengine operating speed include:means for generating an engine speedsignal; threshold generating means for generating a high thresholdrepresentative of a second predetermined speed, in the event that saidoverheated engine condition is not detected, and for generating a lowthreshold representative of said predetermined speed, if said overheatedengine condition is detected; and comparator means being adapted toreceive said engine speed signal at a comparing terminal and said highand low thresholds at a reference terminal, said comparator adapted togenerate a speed reducing signal if the engine speed signal is in excessof the threshold signal being applied to the reference terminal.
 30. Anignition system as set forth in claim 25 wherein said means forgradually reducing engine operating speed includes:a capacitor connectedto said reference terminal which is initially charged to said highthreshold and gradually discharges to said low threshold in the eventsaid overheated engine condition is detected.
 31. An ignition system asset forth in claim 30 wherein:said capacitor has a relatively slowdischarging path which is enabled in the event said overheated enginecondition is detected and a relatively fast charging path which isdisabled in the event an overheated engine condition is detected.
 32. Anignition system as set forth in claim 31 which further includes:anoptically coupled device comprising a light emitting diode connected tosaid means for detecting an overheated engine condition which is adaptedto switch into conduction and energize said light emitting diode in theevent an overheated engine condition is detected, said light emittingdiode being optically coupled to a light sensitive switching device toswitch said discharging path into conduction when said light emittingdiode is energized.
 33. An ignition system as set forth in claim 31which further includes:an optically coupled device comprising a lightemitting diode connected to said means for detecting an overheatedengine condition which is adapted to switch into conduction and energizesaid light emitting diode in the event an overheated engine condition isdetected, said light emitting diode being optically coupled to a lightsensitive switching device to switch said charging path out ofconduction when said light emitting diode is energized.
 34. An ignitionsystem for an internal combustion engine for use in powering a boat orother water vehicle, the ignition system being of the type which has anignition energy storage means, said system comprising:means for chargingthe ignition energy storage means; means for discharging the ignitionenergy storage means; means for detecting an overheated enginecondition; means for reducing the operating speed of the engine byinhibiting the discharging or charging of said ignition energy storagemeans, said reducing means reducing the operating speed to no greaterthan a predetermined speed in the event that said overheated enginecondition is detected while the engine is operating above saidpredetermined speed, and including means for reducing the engineoperating speed to said predetermined speed at a predetermined ratethereby resulting in a gradual reduction in engine operating speed andin a gradual slowing of the boat or other water vehicle when anoverheated engine condition occurs and the engine is operating abovesaid predetermined speed.
 35. An ignition system as set forth in claim34 wherein:said predetermined rate is substantially constant.
 36. Anignition system as set forth in claim 34 wherein:said predetermined ratecauses an exponential decay of the operating speed.
 37. An ignitionsystem as set forth in claim 34 wherein:said predetermined speed isapproximately 2,500 RPM.
 38. An ignition system as set forth in claim 34wherein:said overheated engine condition is a temperature ofapproximately 212° F.
 39. An ignition system as set forth in claim 34wherein:said predetermined rate causes a gradual reduction of engineoperating speed over at least approximately 4 seconds.
 40. An ignitionsystem as set forth in claim 34 wherein said means for reducing engineoperating speed include:means for generating an engine speed signal;threshold generating means for generating a high thresholdrepresentative of a second predetermined speed, in the event that saidoverheated engine condition is not detected, and for generating a lowthreshold representative of said predetermined speed, if said overheatedengine condition is detected; and comparator means being adapted toreceive said engine speed signal at a comparing terminal and said highand low thresholds at a reference terminal, said comparator adapted togenerate a speed reducing signal if the engine speed signal is in excessof the threshold signal being applied to the reference terminal.
 41. Anignition system as set forth in claim 40 wherein said means forgradually reducing engine operating speed include:a capacitor connectedto said reference terminal which is initially charged to said highthreshold and gradually discharges to said low threshold in the eventsaid overheated engine condition is detected.
 42. An ignition system asset forth in claim 41 wherein:said capacitor has a relatively slowdischarging path which is enabled in the event said overheated enginecondition is detected and a relatively fast charging path which isdisabled in the event an overheated engine condition is detected.
 43. Anignition system as set forth in claim 42 which further includes:anoptically coupled device comprising a light emitting diode connected tosaid means for detecting an overheated engine condition which is adaptedto switch into conduction and energize said light emitting diode in theevent an overheated engine condition is detected, said light emittingdiode being optically coupled to a light sensitive switching device toswitch said discharging path into conduction when said light emittingdiode is energized.
 44. An ignition system as set forth in claim 42which further includes:an optically coupled device comprising a lightemitting diode connected to said means for detecting an overheatedengine condition which is adapted to switch into conduction and energizesaid light emitting diode in the event an overheated engine condition isdetected, said light emitting diode being optically coupled to a lightsensitive switching device to switch said charging path out ofconduction when said light emitting diode is energized.